1. Field of the Invention
The present invention relates to an insulated gate bipolar transistor (IGBT) with a trench gate structure.
2. Description of the Related Art
An IGBT is known as a semiconductor device incorporated in an intelligent power module (IPM) for industrial use. For example, in some cases, the IGBT may include a current sense cell for sensing a main current flowing in an active area on the same semiconductor chip along with the IGBT of the active area, as described in JP 2014-229798 A. JP 2014-229798 A discloses a structure in which a p-type diffusion layer, which surrounds the IGBT structure formed in the sensing area, is provided separately from a p-type diffusion layer in the main region implementing the active area of the IGBT.
At the time of assembling the semiconductor package or assembling miscellaneous circuits for application including the IGBT on the customer side, to which the IGBT is delivered, electrostatic discharge (ESD) may occur in the IGBT due to human or mechanical factors. When a voltage equal to or higher than the gate breakdown voltage is applied to the IGBT by ESD, dielectric breakdown may occur in the gate insulating film of the current sense cell, and the main current sensing capability by the current sense cell will be lost. Then, the protection function against the overcurrent of the IGBT will not work sufficiently, and destruction of the IGBT may occur.
In order to increase ESD tolerance, JP 2009-038318 A has proposed a technique to increase the surface area of the gate wiring. In JP 2009-038318 A, the trench gate structure electrically connected to the gate wiring is provided under the gate wiring in the active area of the trench gate IGBT so as to increase the surface area of the gate wiring.
However, as the result of the investigation, when the gate potential is applied to the gate electrode by providing the gate electrode in the region other than the sensing area of the current sense cell using the technique of JP 2009-038318 A, it has been found that the balance of the gate-collector capacitance Cgc between the active area and the current sense cell has collapsed.